Refrigerating device for displaying and preserving perishable goods such as foods, delicacies and the like



March 5, 1935. w. HAMEL TING DEVICE FOR DISPLAYING AND PRESERVING PER1,993,325 ISHABLE REFRIGERA GOODS SUCH AS FOODS, DELICACIES, AND THELIKE Filed Oct. 4, 1933 Patented Mar. 1935 means UNlTED STATES PATENTOFFICE REFRIGEBATING DEVICE FOR DISPLAYING AND PBESEBVING PEBISHABLEGOODS 15.11%): AS FOODS, DELICACIES AND THE Wilhelm Hamel, Amsterdam,Netherlands, as-

signor to Johan Robert Carp, Amsterdam, Netherlands, and Arthur AbrahamRuben,

Berlin-Charlottenburg, Germany Application October 4, 1933, Serial No.692,211

In Great Britain September 18, 1933 8 Claims. (01. 62-895) The inventionrelates to a refrigerating device for displaying and preservingperishable goods such as foods, delicacies and the like, but which mayof course be used also for other cooling purposes. Particularly theinvention relates to devices comprising a surface disposed freely inopen air, on which surface the goods to be cooled are fully exposed toview and which may be of any convenient form, the said surfaceconstituting the member of a refrigerating apparatus that gives 01f thecold, the capacity of said refrigerating apparatus preferably being sogreat that the temperature of the surface can be kept so low that due tothe humidity of the air white frost is formed thereon, the cooling orthe white frosted area being sharply restricted by means of suitableinsulation. In a usual construction hereof the cooling surface on whichthe goods to be cooled are to be placed is surrounded by a frame whichrestricts the cooling or the white frostedarea and which is so wellinsulated from the surface that it will never attain a temperature whichis as low as that of the surface or which is so low that white frost isformed on it. Preferably this frame is made of metal which can easilyassume the temperature of the surrounding air.

In apparatus of the kind referred to the cooled e. g. the white frostedsurface may be used directly for instance as a table, display board, orthe like. The appearance of such a surface is rendered particularlyattractive if white frost is formed thereon, while the cooling effectcan be sufliciently powerful and the use of the apparatus is notassociated with a single difficulty.

In practice it has been shown to be very well possible to insulatetheframe surrounding the white frosted area so well from the coolingsurface that the frame is never covered by white frost itself, when theapparatus is in use. Thus the white frosted area is always sharplyrestricted .by the non-frosted frame which results in the beautifulappearance of the device. It has now appeared, however, that if theatmospl ere is very humid, that is when the air contains a greatquantity of water, this water sometimes condenses on the frame. Thisfact will be understood because the cold which is transmitted from thecooling surface through the insulation to the frame is given off to thesurrounding air and the frame has a temperature which is a little underthat of the surrounding air. The temperature of the frame may, however,be below the dew point of the air and thus water will condense on theframe. This is injurious to the beautiful appearance of the wholeapparatus, as

the frame, when it is made for example of a bright metal, such aschromium, will look very beautiful only if it is dry.

The improvement according to this invention, therefore, resides in theprovision of means for so heating the frame that deposition thereon ofmoisture from the atmosphere is prevented or that such moisture isremoved by evaporation without influencing the white frost on thecooling surface. It will be understood that moisture will be depositedfrom a relatively humid atmosphere upon objects which are colder thanthe. surrounding air, and that a deposition of moisture upon the framecan be prevented by heating the frame to approximately the roomtemperature.

Heating of the frame can be done in many ways. In the first place it ispossible to do it electrically by means of electrical resistances.Furthermore, it is possible to heat the frame by means of the compressedgaseous refrigerating medium, such as S02, which has a considerabletemperature when leaving the compressor of the refrigerating plantbelonging to the. cooling device, and before being cooled down in theordinary manner.

In the drawing a device according to the invention and some details offorms of construction are illustrated by way of example.

Fig. 1 is a diagrammatical representation of a cooling apparatusaccording to the invention which operates with a compressor and in whichthe frame is electrically heated.

Fig. 2 shows a cross section of a construction of the frame surroundingthe cooling surface and restricting the white frosted area, a heatingelement being provided in the form of a special electric cable.

Fig. 3 shows the same construction of insulated frame, but anothermanner of providing an electric heating wire.

Fig. 4 also shows the same cross section, but comprising a tube forguiding the compressed warm refrigerating medium.

In Fig. 1, 1 is the electro-motor, which drives a compressor 3 by meansof a belt transmission 2. The motor 1 also directly drives a fan 4 whichis arranged opposite an air cooled condenser 5. If necessary, this aircooled condenser may of .course be replaced by a water cooled condenser,

in which case the fan 4 may be omitted. The gas (S02, NH: or the like),compressed by the compressor, passes through the piping 6 intothe-cooler 5, from there passes through the piping '7 and then arrivesin the expansion valve (throttling nozzle or the like) 8. The compressedrefrigerhereinafter.

ant is liquefied in the condenser 5 and expands in the expansion valve 8in known manner, thus producing cold which is given off to the plate 9.The expansion valve 8 may, of course, be constructed in various mannersand may, for instance, also be self-regulating. In this case theadjustment can-be controlled either by the gas pressure or by thetemperature of plate 9. After the working medium has given off its cold,it flows through the piping 10 to the suction side of the compressor.The piping 10 is of such length, if necessary arranged in one or morecoils 11, that the working medium is always able, even when thetemperature of the surroundings is low, to give 011 its excessive coldto the surrounding air, (when this cannot be done completely by theplate 9) before it again reaches the compressor 3. At the same time itis thus also possible to give the plate an inclined position, forinstance, because the pipes can then yield suificiently to permit it.

In Fig. 1 the plate 9 is surrounded by a frame 12 which is insulatedfrom the plate and thus cannot assume a low temperature.

The piping coming from the expansion valve 8 may be arranged under theplate 9 in the form of pipe coils, passages or channels in the interiorof the plate 9 or the like. It is recommendable to combine the pointswhere the said piping enters and leaves the plate structure in such amanner that only one opening ought to be made in the table. It is mucheasier then to make the tubes fitting airtight in the opening, which isvery necessary as will, be pointed out It is, of course, important thatthe pipe coil under the plate 9 should be in good thermally conductiveconnection with the said plate 9. This can be done e. g. by soldering orwelding (for example spot welding) when the pipe coil is made as aseparate unit. If necessary, however, the pipe coil may also be integralwith the plate 9, so that so to speak a hollow plate is obtained and therefrigerating medium circulates directly in the plate itself.

It is evident that it is also possible by means of the refrigeratingplant to cool a solution of sodium chloride or the like to, forinstance, 15 C. below zero, and then cause this solution to run alongthe bottom of the plate 9 or to circulate therein. There is therefore acertain accumulation of cold available, and it is then also possible tofit the plate 9 on already existing refrigerating plants. Moreover, thelatter is possible in any case.

In Fig. 1 the plate structure 9, 12 is provided with a cord 31 and aplug 32 for switching on the electrical heating of the frame 12.

Also in Figs. 2, 3 and 4 the plate 9 forms the cooling surface intendedto be covered with white frost and being cooled by means of the pipecoils 22 soldered to the underside of it. The plate 9 is surrounded by aframe 12 preferably made of metal, for example of brass coated withchromium. On the upper side the plate 9 is surrounded by a strip ofrubber or the like 16 (in some cases, for example, also by a rubber tubefilled with cork) against which the plate 9 is pressed by means of thescrews 17. Immediately against the under side of the plate 9 there aredisposed small strips 18 of cork, supported by small strips 19. of wood,against which small plates 20 of fibre, bakelite or the like arepressed. The screws 1'7 co-operate with nuts 21 likewise made ofinsulating material such as fibre or the like. Those nuts 21 are engagedin a groove in the frame 12 in which they can slide endwise. In thismanner the plate 9 can be exactly adjusted and engaged waterandair-tight while a very great resistance is offered to the transmissionof heat between the plates 9 and the frame 12. The resistance is stillfurther increased in that the plate 9 is allowed to come into contactwith the rubber 16 and the cork 18 only along a very narrow edge.

The space below the plate 9 and, therefore, about the pipecoil 22 isfilled with an insulating mass 23, for example cork, the joints of whichare carefully filled up with finer insulating material such as corkpowder, slag wool or the like.

Furthermore, the whole is closed by a plate 24 so as to form an airandwater-tight unit. It is of importance, of course, that no air can enterinto the space between the plates 9 and 24 because if there should arisesome circulation of air white frost would be formed there also and thiswould decrease the cooling action at the upper side considerably, whileas well a lot of condensation water could be formed within theinsulating mass.

In Fig. 2 there is located at the inner side of the frame, thus hiddenfrom view, an electric cable, 25 which e. g. is connected to the cord 31in Fig. 1. This cable may be, for example, a lead covered cablecomprising a core of asbestos on which a wire is helically wound, thesaid wire being made of a high resistant metal. This heating element issurrounded by specially prepared rubber and then covered with the lead.The cable also could be formed, of course, by a simple straight wire,embedded in the specially prepared rubber and covered by the lead.Dependent on the electric voltage used, the temperature 01' the framecan be regulated. Also electric resistances, switches or the like can beprovided to control the heating of the frame or the cord 31 may beconnected to the circuit of the motor 1, so that heating of the frameonly is switched on when this motor is running.

It is not necessary, moreover, to provide the heating cable 25 or thelike along the whole length of the frame and often it is sufficient toheat only one part of the frame which it is particularly desired shouldnot become wetted. In Fig. 1 it is shown furthermore how the cable 25 isfastened by means of a strip 26 of insulating material.

In Fig. 3 is shown how a simple electric heating wire 30 can be enclosedbetween two strips of asbestos 27 and 28 for the purpose of theinvention.

In Fig. 4 a tube 29 adapted to be connected to the outlet of thecompressor of the refrigerating plant is soldered to the inner side ofthe frame. In this event the piping 6 in Fig. 1 immediately afterleaving the compressor 3 is connected to the tube 29 in Fig. 4, theoutlet of which thereafter is connected to the cooler 5, or directly tothe valve 8 if the refrigerating medium after having passed the tube 29and being cooled down therein, needs no further cooling in a cooler suchas 5.

It will be understood that at all events it is not permitted that theheat developed by the means described above be so great that white froston the surface of the plate 9 is influenced.

A special advantage of the heating elements above described is in thefollowing:

If by some reason, say accidentally, humidity has deposited within theplate unit, so that, for example, the insulating mass 23 contains water,it is possible to remove this water by evaporation by heating the frameand thus the plate by the heating means described above. Preferablycooling is interrupted then, that is to say the refrigerating machine isstopped and the snow layer removed. It is also possible to heat morestrongly in this event, for example by increasing the electric voltagein apparatus as shown in Figs. 2 and 3.

It is not necessary, of course, to heat the frame for the reasonsmentioned above by means arranged internally of the frame (electricresistance wires, compressed medium piping). Heating may also occur byexternal means, e. g. there may be arranged electric or other lampsalong the outside of the frame forthis purpose. Besides giving undercircumstances a very decorative effect, the radiating or direct heat ofthese lamps may be used for heating the frame.

What I claim is:-

1. In a refrigerated device for displaying and preserving perishablegoods, a cooling member having its upper surface freely exposed in openair and adapted to have the goods placed thereon, refrigerating meansfor cooling said member to below that temperature at which moisture willbe deposited on said member from air circulating over the same, a framesurrounding said member to define the limits of the exposed coolingsurface thereof, heat insulating means between said frame and coolingmember, and means for heating said frame to prevent the deposition ofmoisture thereon from the atmosphere.

2. In a refrigerated device for displaying and preserving perishablegoods, a cooling member having its upper surface freely exposed in openair and adapted to have the goods placed thereon, refrigerating meansfor cooling said member, a heat-conducting frame surrounding said memberto define the limits of the exposed cooling surface thereof, heatinsulating means between said frame and cooling member, and heatingmeans concealed from view within said frame for heating the latter toprevent the deposition of moisture thereon from the atmosphere.

3. In a refrigerated device for displaying and preserving perishablegoods, a cooling member having its upper surface freely exposed in openair and adapted to have the goods placed thereon, refrigerating meansfor cooling said membeer to maintain a deposit of frost thereon bymoisture withdrawn from air circulating over said cooling member, aframe surrounding said member to define the limits of the frosted areathereof, heat insulating means between said frame and cooling member,and electrical heating means concealed from view within said frame forheating the latter to prevent the deposition of moisture thereon fromthe atmosphere.

4. In a refrigerated device for displaying and preserving perishablegoods, a cooling member having its upper surface freely exposed in openair and adapted to have the goods placed thereon, refrigerating meansfor cooling said member, a metallic frame surrounding said member todefine the limits of the exposed cooling surface thereof, heatinsulating means between said frame and cooling member, and insulatedcables containing electrical heating wires within said frame andextending along the inner side thereof.

5. In a refrigerated device for displaying and preserving perishablegoods, a cooling member having its upper surface freely exposed in openair and adapted to have the goods placed thereon, refrigerating meansfor cooling said member, a metallic frame surrounding said member todefine the limits of the exposed cooling surface thereof, heatinsulating means between said frame and cooling member, electric heatingwires within said frame, and a lead covering enclosing and insulatedfrom said wires, said heating wires extending along and with the leadcovering thereof adjacent the inner side of said frame.

6. In a refrigerated device for displaying and preserving perishablegoods, a cooling member having its upper surface freely exposed in openair and adapted to have the goods placed thereon, refrigerating meansincluding a compressor and condenser for cooling said cooling member bythe expansion of a gaseous refrigerating medium, said refrigeratingmeans being of sufficient capacity to maintain a coating of white froston said cooling member by moisture withdrawn from air circulating overthe same, a frame surrounding said cooling member to define the limitsof the exposed cooling surface thereof, thermal insulation between saidframe and cooling member, and means for passing the compressed gasesfrom said compressor through said frame, thereby to heat the latter to atemperature above the dew point of the surrounding air.

7. A device for displaying and preserving perishable goods comprising adisplay surface freely exposed in open air, means for refrigerating saidsurface, a metallic frame surrounding said surface to define the exposedcooling portion upon which goods may be placed, thermal insulationbetween said frame and surface, and heating means concealed from viewwithin said frame to prevent the formation of dew upon the metallicframe.

8. In a device for the preservation and display of perishable goods, thecombination with a substantially air-tight body comprising a frame, aplate forming the upper surface of the body, refrigerating conduitswithin the body and in heattransfer relationship to said plate, a layerof heat insulating material within said frame beneath said plate andadjacent said conduits, and means insulating said frame from said plateto prevent cooling of said frame low enough for the deposition of hoarfrost thereon, of refrigerating apparatus for supplying a refrigeratingmedium to said conduits in quantity sufficient to maintain a coating ofwhite frost upon said plate by moisture withdrawn from air circulatingover the same, and heating means within said body to evaporate therefromany moisture which may collect within the same and to heat the frame toa temperature above that at which moisture may deposit upon the samefrom the surrounding air.

WILHELM HAMIEL.

